Given the litigious climate we live in, my guess is that that Ken/Billy have decided that rebreathers or EANx aren't worth the exposure.

I remember years ago when many dive boats wouldn't allow anything but air tanks on board. The argument against enriched EANx was that "bad" things tend to happen at depth, while, for the most part, on air, "bad" things happen at the surface. Given the safe use of EANx for many years, IMHO, this argument is very weak.

Rebreathers, on the other hand, have a history of killing divers. The risk of death or injury, while low, is higher than any of us like to see and unacceptable to many.

While divers sign waivers, these waivers don't prevent lawsuits and monetary judgements. I used to be a DM; no longer. I wouldn't want to be the DM, boat captain or store owner should someone on my dive trip have an accident. If Ken/Billy want to minimize their exposure by not allowing EANx or rebreathers on their trips, that's their call.

I hope that Ken/Billy will reevaluate their ban on "nitrox." But, until they do, it's their call.